The present invention relates to a curing composition which is useful for various uses such as molding materials and coatings, etc. In more detail, it relates to a curing composition composed of a compound (A) having at least two 2-oxazoline groups, a compound (B) having at least two functional groups of one or a plural kind selected from the group consisting of an aromatic hydroxyl group, an amino group and a thiol group, and an onium salt catalyst (C). Also, the present invention relates to a catalyst for the reaction of a compound (A) having at least two 2-oxazoline groups with a compound (B) having at least two functional groups of one or a plural kind selected from the group consisting of an aromatic hydroxyl group, an amino group and a thiol group, wherein the catalyst is an onium salt which is comprised of a cationic onium moiety and a counteranion. Furthermore, the present invention relates to a molded article prepared by curing a composition composed of a compound (A) having at least two 2-oxazoline groups, a compound (B) having at least two functional groups of one or a plural kind selected from the group consisting of an aromatic hydroxyl group, an amino group and a thiol group, and an onium salt catalyst (C).
It is known that a 2-oxazoline group reacts with a compound having an aromatic hydroxyl group in a ring opening type mechanism to provide an ether-amide. EQU --CONH--CR(R')--CR"(R"')--O--Ph
The method for preparing polymeric materials or crosslinked resins in accordance with the reaction is also known. Thus, the process to prepare a crosslinked resin by subjecting a mixture of a bis-2-oxazoline and a polymer having aromatic hydroxyl groups to reaction in the presence of a catalyst selected from a group consisting of phosphorous acid, organic phosphites and oxazoline ring-opening polymerization catalysts is exemplified in U.S. Pat. No. 4,843,142. Also, a poly(ether-amide) prepared by the step-growth polymerization reaction of an oxazoline compound with a phenolic resin is exemplified in U.S. Pat. No. 4,430,491. The other catalysts for the same reaction have been reported, for example, an alkali or an alkaline earth metal cationic complex in U.S. Pat. No. 4,613,662: a phosphite in U.S. Pat. No. 4,699,970; a triphenylmethyl carbonium ion salt in U.S. Pat. No. 4,746,719; and a phosphine catalyst in U.S. Pat. No. 4,748,230.
It is also known that a 2-oxazoline reacts with a compound having a thiol (mercapto) group to provide a thioether-amide. EQU --CONH--CR(R')--CR"(R"')--S--
The process to prepare a thermosetting resin by subjecting a mixture of a bisoxazoline compound and a polythiol compound to reaction in the presence of an alkali metal cationic complex is exemplified in U.S. Pat. No. 4,737,574.
It is also known that a 2-oxazoline group reacts with a compound having an amino group to provide an amino-amide. EQU --CONH--CR(R')--CR"(R"')--NR""--
The process to prepare a thermosetting resin by subjecting a mixture of a bisoxazoline and an aromatic polyamine to reaction with heating in the presence of oxazoline ring-opening polymerization catalysts is exemplified in U.S. Pat. No. 4,837,302.
In these previous arts, a catalyst effective to the reaction of an oxazoline with a functional group differs from a catalyst for another functional group. Catalysts effective to the reaction of an oxazoline with various functional groups have not been known before those provided in the present invention.